All human being and living creatures are made up of cell. It is the fundamental building blocks of life. Cells vary to form individual organisms to multi-cellular structures. Cells are made up of 90% fluid called cytoplasm which consists of free amino acid, proteins, carbohydrates, fats and numerous molecules. Cell environment affect gene expression/ regulation, and thus are very important aspects of inheritance. We understand that the function of cells has come from careful examination of cellular structure. For more than a century, light microscope has been used to study cells. Most cell biology students are familiar with the use of light microscope, having observed some cells in their biology courses. They used the microscope as a research tool to reveal cellular structure and to explore the properties and functions of the cells.
The importance of microscopy as a method to study cells has been overshadowed, to some extent, by methods of molecular biology. However, the microscope remains an important tool. Recent advances in microscopy, particularly the use of fluorescent probes to study cell function in living cells, are bringing microscopy back into the forefront of research in cell biology. Light microscope relies on the simple principle of magnification; an object is magnified in size so that it becomes visible to the observer. There is a limit to the useful magnification that can be achieved in a light microscope because of the limitations in the resolving power of the lenses.
There is a limit in the ability to resolve two separate objects as distinct structures. To view cell structures using light microscope, biologists developed many dyes or strains that either stain whole cell or preferentially stain various organelles within the cell. Like methylene blue stains the nucleus of a cell blue. Various chemicals, including glutaraldehyde or alcohol, are used to cross-link cellular protein and to stabilize cells more or less permanently. Such techniques will be used in cell biology course. For past three or four decades several techniques have enhanced the effectiveness of the light microscopy. It includes phase contrast microscopy, Nomarski differential interference contrast microscopy and Hoffman Modulation Contrast microscopy. These allow cell biologist to examine structures in the living cell without fixing the cell or using staining agents.
The advantages of contrasting enhancing microscopy will become apparent during examination of cells in the laboratory. In addition to light microscopy, fluorescence microscopy has become an important research tool. Cells have complex interactions with the surrounding environment. Whether it is the external world of a single celled organism or the other cells of a multi-cellular organism, a complex web of interactions is present. Study of the mechanisms by which cells respond appropriately to their environments is a major part of cell biology research and often such studies involve what is called signal transduction. For example, a hormone such as insulin interacting with the surface of a cell can result in the altered behavior of hundreds of molecular components inside the cells.
This sort of complex and finely tuned cell response to an external signal is required for normal metabolism and to prevent metabolic disorders like Type II Diabetes Mellitus. Cells of a multi-cellular organism have the same genetic material in every cell, yet, there are over 200 types of cell in the body that are different shapes, sizes and carry out very different functions. ALL of these cells were developed from one special cell called zygote. The study of how the many cell types develop during embryonic development is a branch of Biology that is heavily dependent on the use of microscopy. Much of the control of cell differentiation is at the level of the control of gene transcription the control of which mRNA are made. Muscle cells make muscle proteins and nerve cells make brain proteins. Geneticists, molecular biologists and cell biologists are working to discover the details of how cells specialize to accomplish hundreds of functions from muscle contraction to memory storage.
